A vehicle's state conditions such as inertial parameters may vary from different driving conditions such as the number of passengers and the seating arrangement. Variation in the vehicle's inertial parameters may consequently affect the accuracy of vehicle state estimator models that are employed in vehicle control and stability systems. It is, accordingly, desirable to be able to compensate in real time for variation in a vehicle's inertial parameters in vehicle state estimators. Real time knowledge of such inertial variations is useful in many active vehicle safety applications, including yaw stability control and rollover prevention.